The IP pool configuration file is used for defining a single object that contains a reference to multiple IP address/netmask pairs. A pool can consist of a mixture of netmask sizes, from 0 to 32.

In the current release, only IPv4 addressing is supported in IP pools.

The IP pool configuration file provides for defining two different mechanisms for improving speed in matching IP addresses with rules. The first, table, defines a lookup table to provide a single reference in a filter rule to multiple targets. The second mechanism, group-map, provides a mechanism to target multiple groups from a single filter line.

The group-map command can be used only with filter rules that use the call command to invoke either fr_srcgrpmap or fr_dstgrpmap, to use the source or destination address, respectively, for determining which filter group
to jump to next for continuation of filter packet processing.

Pool Types

Two storage formats are provided: hash tables and tree structure. The hash table is intended for use with objects that all contain the same netmask or a few, different sized-netmasks of non-overlapping address space. The tree is designed for supporting exceptions to a covering mask, in addition
to normal searching as you would do with a table. It is not possible to use the tree data storage type with group-map configuration entries.

Pool Roles

When a pool is defined in the configuration file, it must have an associated role. At present the only supported role is ipf. Future development might see further expansion of the use of roles by other sections of IPFilter code.

Examples

The following examples show how the pool configuration file is used with the ipf configuration file to enhance the succinctness of the latter file's entries.

Example 1 Referencing Specific Pool

The following example shows how a filter rule makes reference to a specific pool for matching of the source address.

pass in from pool/100 to any

The following pool configuration matches IP addresses 1.1.1.1 and any in 2.2.0.0/16, except for those in 2.2.2.0/24.

Example 2 ipf Configuration Entry

The following ipf.conf excerpt uses the fr_srcgrpmap/fr_dstgrpmap lookups to use the group-map facility to look up the next group to use for filter processing, providing the call filter rule is matched.

call now fr_srcgrpmap/1010 in all
call now fr_dstgrpmap/2010 out all
pass in all group 1020
block in all group 1030
pass out all group 2020
block out all group 2040

An ippool configuration to work with the preceding ipf.conf segment might look like the following: